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Abstract

Polarization entangled photon pair source is widely used in many quantum information processing applications such as teleportation, quantum communications, quantum computation and high precision quantum metrology. We report on the generation of a continuous-wave pumped 1550 nm polarization entangled photon pair source at telecom wavelength using a type-II periodically poled KTiOPO4 (PPKTP) crystal in a Sagnac interferometer. Hong-Ou-Mandel (HOM) interference measurement yields signal and idler photon bandwidth of 2.4 nm. High quality of entanglement is verified by various kinds of measurements, for example two-photon interference fringes, Bell inequality and quantum states tomography. The source can be tuned over a broad range against temperature or pump power without loss of visibilities. This source will be used in our future experiments such as generation of orbital angular momentum entangled source at telecom wavelength for quantum frequency up-conversion, entanglement based quantum key distributions and many other quantum optics experiments at telecom wavelengths.

Coincidence counts in 10 second as a function of the displacement of the adjustable air gap. Error bars are estimated from multiple measurements; the experimental data is fitted using triangle function.

Two photon coincidence in 10s as a function of the angle the two HWPs. The background dark coincidence is not subtracted; error bars are obtained from multiple measurements; the data sets are fitted using sinusoidal function.

(a)Visibilities as a function of pump beam power, the power is varying from 15 mW to 120 mW; (b) visibilities as a function of crystal temperature, the temperature is tuning from 15 °C to 55 °C. The error bars are obtained from multiple measurements.